Various kinds of displays which are mounted on the head to display images from a computer or a video device, that is, head mount displays are known. For example, in Japanese Patent Application Laid-Open No. 5-134208, it is proposed to use an elliptical body having two focal points in order to make a display small. That is, a part of the ellipse is used to form a concave mirror, so that light having passed through the display device and an eccentric lens group goes through a first focal point of the ellipse, and light reflected on the concave mirror goes through a second focal point, and the observer's eye is placed at the second focal point (see FIG. 1 in the above publication). In this manner, the light having passed through the first focal point is reflected on the concave mirror, and reliably passes through the second focal point to enter the observer's eye.
In the display disclosed in the above publication, however, when the observer mounts the display, the display device and the eccentric lens group are located at the side of the observer's eye, and there is the possibility that these may interfere with the observer's temporal region (a region near the ear). Therefore, it is necessary to construct the display such that the display device and the eccentric lens group do not interfere with the observer's temporal region.
In the configuration which uses two focal points of the ellipse, the display screen is likely to be distorted. That is, the angle of light emanated from the first focal point does not become the same as the angle of light gathered by the second focal point. Therefore, it is necessary to arrange a plurality of complicated eccentric lenses as the eccentric lens group in the vicinity of the display device, in order to match the angle of light entering the eye with the angle of light having passed through the display device. Hence, it is quite difficult to decrease the size of the display so as to be able to mount it on the head.